System and method of implementation of interferometric modulators for display mirrors

ABSTRACT

A specular interferometric modulator array is configured to be at least partially selectably reflective. As such, the array forms a mirror surface having the capability of displaying information to the user while simultaneously being used as a specular mirror. The displayed information may be based on information from an external source, may be programmable, and may be based on user input.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.60/613,298, titled “System and Method for Implementation ofInterferometric Modulator Displays,” filed Sep. 27, 2004, which isincorporated by reference, in its entirety.

BACKGROUND

1. Field of the Invention

The field of the invention relates to microelectromechanical systems(MEMS).

2. Description of the Related Technology

Microelectromechanical systems (MEMS) include micro mechanical elements,actuators, and electronics. Micromechanical elements may be createdusing deposition, etching, and or other micromachining processes thatetch away parts of substrates and/or deposited material layers or thatadd layers to form electrical and electromechanical devices. One type ofMEMS device is called an interferometric modulator. As used herein, theterm interferometric modulator or interferometric light modulator refersto a device that selectively absorbs and/or reflects light using theprinciples of optical interference. In certain embodiments, aninterferometric modulator may comprise a pair of conductive plates, oneor both of which may be transparent and/or reflective in whole or partand capable of relative motion upon application of an appropriateelectrical signal. In a particular embodiment, one plate may comprise astationary layer deposited on a substrate and the other plate maycomprise a metallic membrane separated from the stationary layer by anair gap. As described herein in more detail, the position of one platein relation to another can change the optical interference of lightincident on the interferometric modulator. Such devices have a widerange of applications, and it would be beneficial in the art to utilizeand/or modify the characteristics of these types of devices so thattheir features can be exploited in improving existing products andcreating new products that have not yet been developed.

Summary of Certain Embodiments

The system, method, and devices of the invention each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention, its moreprominent features will now be discussed briefly. After considering thisdiscussion, and particularly after reading the section entitled“Detailed Description of Certain Embodiments” one will understand howthe features of this invention provide advantages over other displaydevices.

One embodiment comprises a device with a substrate, and an array ofreflective elements arranged on the substrate to form a mirror surfacethat specularly reflects incident light in at least one wavelength band,each element comprising a partially reflective layer, and asubstantially reflective layer separated from the partially reflectivelayer by a predetermined space, wherein the space defines aninterferometric cavity wherein one or more of the elements areconfigured to be selectably reflective; and wherein one or more of theelements are configured to be permanently reflective.

Another embodiment provides a vehicle comprising a steering mechanism,and a mirror configured to be positioned such that light coming frombehind the vehicle is reflected to a location for an operator to seewhen positioned to use the steering mechanism, the mirror comprising asubstrate, and an array of reflective elements arranged on the substrateto form a mirror surface that specularly reflects incident light in atleast one wavelength band, each element comprising a partiallyreflective layer, and a substantially reflective layer separated fromthe partially reflective layer by a predetermined space, wherein thespace defines an interferometric cavity.

Still another embodiment provides a device comprising a mirrorcomprising a substrate, and an array of reflective elements arranged onthe substrate to form a mirror surface that specularly reflects incidentlight in at least one wavelength band, each element comprising apartially reflective layer, and a substantially reflective layerseparated from the partially reflective layer by a predetermined space,wherein the space defines an interferometric cavity and the wavelengthband of light reflected from the element is based on a dimension of thecavity, and a mount configured to attach the mirror to a vehicle, awall, an article of furniture, an ornamental object, an article ofclothing, or a person.

Still another embodiment provides a device, comprising means forsupporting; and means for specularly reflecting incident light in atleast one wavelength band and being formed on the supporting means,wherein a first portion of the reflecting means is selectably reflectiveand a second portion of the reflecting means is permanently reflective.

Still another embodiment provides a method of using a device comprisinga mirror comprising a substrate; and an array of reflective elementsarranged on the substrate to form a mirror surface that specularlyreflects incident light in at least one wavelength band, each elementcomprising: a partially reflective layer; and a substantially reflectivelayer separated from the partially reflective layer by a predeterminedspace, wherein the space defines an interferometric cavity and thewavelength band of light reflected from the element is based on adimension of the cavity; and a mount configured to attach the mirror toa vehicle, a wall, an article of furniture, an ornamental object, anarticle of clothing, or a person, the method comprising establishing acommunication link between the device and an information source,receiving data from the source, and displaying the data on the array.

Another embodiment provides a method of manufacturing a devicecomprising forming a substrate, and fashioning an array of reflectiveelements arranged on the substrate to form a mirror surface thatspecularly reflects incident light in at least one wavelength band, eachelement comprising: a partially reflective layer, a substantiallyreflective layer separated from the partially reflective layer by apredetermined space, wherein the space defines an interferometriccavity, wherein one or more of the elements are configured to beselectably reflective, and wherein one or more of the elements areconfigured to be permanently reflective.

Another embodiment provides a device manufactured by a processcomprising: forming a substrate, and fashioning an array of reflectiveelements arranged on the substrate to form a mirror surface thatspecularly reflects incident light in at least one wavelength band, eachelement comprising: a partially reflective layer, a substantiallyreflective layer separated from the partially reflective layer by apredetermined space, wherein the space defines an interferometriccavity, wherein one or more of the elements are configured to beselectably reflective, and wherein one or more of the elements areconfigured to be permanently reflective.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view depicting a portion of one embodiment of aninterferometric modulator display in which a movable reflective layer ofa first interferometric modulator is in a relaxed position and a movablereflective layer of a second interferometric modulator is in an actuatedposition.

FIG. 2 is a system block diagram illustrating one embodiment of anelectronic device incorporating a 3x3 interferometric modulator display.

FIG. 3 is a diagram of movable mirror position versus applied voltagefor one exemplary embodiment of an interferometric modulator of FIG. 1.

FIG. 4 is an illustration of a set of row and column voltages that maybe used to drive an interferometric modulator display.

FIGS. 5A and 5B illustrate one exemplary timing diagram for row andcolumn signals that may be used to write a frame of display data to the3×3 interferometric modulator display of FIG. 2.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment ofa visual display device comprising a plurality of interferometricmodulators.

FIG. 7A is a cross section of the device of FIG. 1.

FIG. 7B is a cross section of an alternative embodiment of aninterferometric modulator.

FIG. 7C is a cross section of another alternative embodiment of aninterferometric modulator.

FIG. 7D is a cross section of yet another alternative embodiment of aninterferometric modulator.

FIG. 7E is a cross section of an additional alternative embodiment of aninterferometric modulator.

FIG. 8 is a front view of an interferometric device configured as aspecular reflective display that can provide information to a viewer.

FIG. 9 is a front view of a rear-view mirror embodiment.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following detailed description is directed to certain specificembodiments of the invention. However, the invention can be embodied ina multitude of different ways. In this description, reference is made tothe drawings wherein like parts are designated with like numeralsthroughout. As will be apparent from the following description, theembodiments may be implemented in any device that is configured todisplay an image, whether in motion (e.g., video) or stationary (e.g.,still image), and whether textual or pictorial. More particularly, it iscontemplated that the embodiments may be implemented in or associatedwith a variety of electronic devices such as, but not limited to, mobiletelephones, wireless devices, personal data assistants (PDAs), hand-heldor portable computers, GPS receivers/navigators, cameras, MP3 players,camcorders, game consoles, wrist watches, clocks, calculators,television monitors, flat panel displays, computer monitors, autodisplays (e.g., odometer display, etc.), cockpit controls and/ordisplays, display of camera views (e.g., display of a rear view camerain a vehicle), electronic photographs, electronic billboards or signs,projectors, architectural structures, packaging, and aestheticstructures (e.g., display of images on a piece of jewelry). MEMS devicesof similar structure to those described herein can also be used innon-display applications such as in electronic switching devices.

One interferometric modulator display embodiment comprises an array ofMEMS display elements, at least a portion of which are substantiallyspecular, and at least a portion of which are selectably reflective. Theportion of the display which is specular may be used as a mirror, andthe selectably reflective portion may be used to display information.This allows for information to be displayed on the device while it issimultaneously being used as a mirror, for example, while driving,combing one's hair or applying make-up.

One interferometric modulator display embodiment comprising aninterferometric MEMS display element is illustrated in FIG. 1. In thesedevices, the pixels are in either a bright or dark state. In the bright(“on” or “open”) state, the display element reflects a large portion ofincident visible light to a user. When in the dark (“off” or “closed”)state, the display element reflects little incident visible light to theuser. Depending on the embodiment, the light reflectance properties ofthe “on” and “off” states may be reversed. MEMS pixels can be configuredto reflect predominantly at selected colors, allowing for a colordisplay in addition to black and white.

FIG. 1 is an isometric view depicting two adjacent pixels in a series ofpixels of a visual display, wherein each pixel comprises a MEMSinterferometric modulator. In some embodiments, an interferometricmodulator display comprises a row/column array of these interferometricmodulators. Each interferometric modulator includes a pair of reflectivelayers positioned at a variable and controllable distance from eachother to form a resonant optical cavity with at least one variabledimension. In one embodiment, one of the reflective layers may be movedbetween two positions. In the first position, referred to herein as therelaxed position, the movable reflective layer is positioned at arelatively large distance from a fixed partially reflective layer. Inthe second position, referred to herein as the actuated position, themovable reflective layer is positioned more closely adjacent to thepartially reflective layer. Incident light that reflects from the twolayers interferes constructively or destructively depending on theposition of the movable reflective layer, producing either an overallreflective or non-reflective state for each pixel.

The depicted portion of the pixel array in FIG. 1 includes two adjacentinterferometric modulators 12 a and 12 b. In the interferometricmodulator 12 a on the left, a movable reflective layer 14 a isillustrated in a relaxed position at a predetermined distance from anoptical stack 16 a, which includes a partially reflective layer. In theinterferometric modulator 12 b on the right, the movable reflectivelayer 14 b is illustrated in an actuated position adjacent to theoptical stack 16 b.

The optical stacks 16 a and 16 b (collectively referred to as opticalstack 16), as referenced herein, typically comprise of several fusedlayers, which can include an electrode layer, such as indium tin oxide(ITO), a partially reflective layer, such as chromium, and a transparentdielectric. The optical stack 16 is thus electrically conductive,partially transparent and partially reflective, and may be fabricated,for example, by depositing one or more of the above layers onto atransparent substrate 20. In some embodiments, the layers are patternedinto parallel strips, and may form row electrodes in a display device asdescribed further below. The movable reflective layers 14 a, 14 b may beformed as a series of parallel strips of a deposited metal layer orlayers. (orthogonal to the row electrodes of 16 a, 16 b) deposited ontop of posts 18 and an intervening sacrificial material depositedbetween the posts 18. When the sacrificial material is etched away, themovable reflective layers 14 a, 14 b are separated from the opticalstacks 16 a, 16 b by a defined gap 19. A highly conductive andreflective material such as aluminum may be used for the reflectivelayers 14, and these strips may form column electrodes in a displaydevice.

With no applied voltage, the cavity 19 remains between the movablereflective layer 14 a and optical stack 16 a, with the movablereflective layer 14 a in a mechanically relaxed state, as illustrated bythe pixel 12 a in FIG. 1. However, when a potential difference isapplied to a selected row and column, the capacitor formed at theintersection of the row and column electrodes at the corresponding pixelbecomes charged, and electrostatic forces pull the electrodes together.If the voltage is high enough, the movable reflective layer 14 isdeformed and is forced against the optical stack 16. A dielectric layer(not illustrated in this Figure) within the optical stack 16 may preventshorting and control the separation distance between layers 14 and 16,as illustrated by pixel 12 b on the right in FIG. 1. The behavior is thesame regardless of the polarity of the applied potential difference. Inthis way, row/column actuation that can control the reflective vs.non-reflective pixel states is analogous in many ways to that used inconventional LCD and other display technologies.

FIGS. 2 through 5 illustrate one exemplary process and system for usingan array of interferometric modulators in a display application.

FIG. 2 is a system block diagram illustrating one embodiment of anelectronic device that may incorporate aspects of the invention. In theexemplary embodiment, the electronic device includes a processor 21which may be any general purpose single- or multi-chip microprocessorsuch as an ARM, Pentium®, Pentium II®, Pentium III®, Pentium IV®,Pentium® Pro, an 8051, a MIPS®, a Power PC®, an ALPHA®, or any specialpurpose microprocessor such as a digital signal processor,microcontroller, or a programmable gate array. As is conventional in theart, the processor 21 may be configured to execute one or more softwaremodules. In addition to executing an operating system, the processor maybe configured to execute one or more software applications, including aweb browser, a telephone application, an email program, or any othersoftware application.

In one embodiment, the processor 21 is also configured to communicatewith an array driver 22. In one embodiment, the array driver 22 includesa row driver circuit 24 and a column driver circuit 26 that providesignals to a panel or display array (display) 30. The cross section ofthe array illustrated in FIG. 1 is shown by the lines 1-1 in FIG. 2. ForMEMS interferometric modulators, the row/column actuation protocol maytake advantage of a hysteresis property of these devices illustrated inFIG. 3. It may require, for example, a 10 volt potential difference tocause a movable layer to deform from the relaxed state to the actuatedstate. However, when the voltage is reduced from that value, the movablelayer maintains its state as the voltage drops back below 10 volts. Inthe exemplary embodiment of FIG. 3, the movable layer does not relaxcompletely until the voltage drops below 2 volts. There is thus a rangeof voltage, about 3 to 7 V in the example illustrated in FIG. 3, wherethere exists a window of applied voltage within which the device isstable in either the relaxed or actuated state. This is referred toherein as the “hysteresis window” or “stability window.” For a displayarray having the hysteresis characteristics of FIG. 3, the row/columnactuation protocol can be designed such that during row strobing, pixelsin the strobed row that are to be actuated are exposed to a voltagedifference of about 10 volts, and pixels that are to be relaxed areexposed to a voltage difference of close to zero volts. After thestrobe, the pixels are exposed to a steady state voltage difference ofabout 5 volts such that they remain in whatever state the row strobe putthem in. After being written, each pixel sees a potential differencewithin the “stability window” of 3-7 volts in this example. This featuremakes the pixel design illustrated in FIG. 1 stable under the sameapplied voltage conditions in either an actuated or relaxed pre-existingstate. Since each pixel of the interferometric modulator, whether in theactuated or relaxed state, is essentially a capacitor formed by thefixed and moving reflective layers, this stable state can be held at avoltage within the hysteresis window with almost no power dissipation.Essentially no current flows into the pixel if the applied potential isfixed.

In typical applications, a display frame may be created by asserting theset of column electrodes in accordance with the desired set of actuatedpixels in the first row. A row pulse is then applied to the row 1electrode, actuating the pixels corresponding to the asserted columnlines. The asserted set of column electrodes is then changed tocorrespond to the desired set of actuated pixels in the second row. Apulse is then applied to the row 2 electrode, actuating the appropriatepixels in row 2 in accordance with the asserted column electrodes. Therow 1 pixels are unaffected by the row 2 pulse, and remain in the statethey were set to during the row 1 pulse. This may be repeated for theentire series of rows in a sequential fashion to produce the frame.Generally, the frames are refreshed and/or updated with new display databy continually repeating this process at some desired number of framesper second. A wide variety of protocols for driving row and columnelectrodes of pixel arrays to produce display frames are also well knownand may be used in conjunction with the present invention.

FIGS. 4 and 5 illustrate one possible actuation protocol for creating adisplay frame on the 3×3 array of FIG. 2. FIG. 4 illustrates a possibleset of column and row voltage levels that may be used for pixelsexhibiting the hysteresis curves of FIG. 3. In the FIG. 4 embodiment,actuating a pixel involves setting the appropriate column to −V_(bias),and the appropriate row to +ΔV, which may correspond to −5 volts and +5volts respectively Relaxing the pixel is accomplished by setting theappropriate column to +V_(bias), and the appropriate row to the same+ΔV, producing a zero volt potential difference across the pixel. Inthose rows where the row voltage is held at zero volts, the pixels arestable in whatever state they were originally in, regardless of whetherthe column is at +V_(bias), or −V_(bias). As is also illustrated in FIG.4, it will be appreciated that voltages of opposite polarity than thosedescribed above can be used, e.g., actuating a pixel can involve settingthe appropriate column to +V_(bias), and the appropriate row to −ΔV. Inthis embodiment, releasing the pixel is accomplished by setting theappropriate column to −V_(bias), and the appropriate row to the same−ΔV, producing a zero volt potential difference across the pixel.

FIG. 5B is a timing diagram showing a series of row and column signalsapplied to the 3×3 array of FIG. 2 which will result in the displayarrangement illustrated in FIG. 5A, where actuated pixels arenon-reflective. Prior to writing the frame illustrated in FIG. 5A, thepixels can be in any state, and in this example, all the rows are at 0volts, and all the columns are at +5 volts. With these applied voltages,all pixels are stable in their existing actuated or relaxed states.

In the FIG. 5A frame, pixels (1,1), (1,2), (2,2), (3,2) and (3,3) areactuated. To accomplish this, during a “line time” for row 1, columns 1and 2 are set to −5 volts, and column 3 is set to +5 volts. This doesnot change the state of any pixels, because all the pixels remain in the3-7 volt stability window. Row 1 is then strobed with a pulse that goesfrom 0, up to 5 volts, and back to zero. This actuates the (1,1) and(1,2) pixels and relaxes the (1,3) pixel. No other pixels in the arrayare affected. To set row 2 as desired, column 2 is set to −5 volts, andcolumns 1 and 3 are set to +5 volts. The same strobe applied to row 2will then actuate pixel (2,2) and relax pixels (2,1) and (2,3). Again,no other pixels of the array are affected. Row 3 is similarly set bysetting columns 2 and 3 to −5 volts, and column 1 to +5 volts. The row 3strobe sets the row 3 pixels as shown in FIG. 5A. After writing theframe, the row potentials are zero, and the column potentials can remainat either +5 or −5 volts, and the display is then stable in thearrangement of FIG. 5A. It will be appreciated that the same procedurecan be employed for arrays of dozens or hundreds of rows and columns. Itwill also be appreciated that the timing, sequence, and levels ofvoltages used to perform row and column actuation can be varied widelywithin the general principles outlined above, and the above example isexemplary only, and any actuation voltage method can be used with thesystems and methods described herein.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment ofa display device 40. The display device 40 can be, for example, acellular or mobile telephone. However, the same components of displaydevice 40 or slight variations thereof are also illustrative of varioustypes of display devices such as televisions and portable media players.

The display device 40 includes a housing 41, a display 30, an antenna43, a speaker 45, an input device 48, and a microphone 46. The housing41 is generally formed from any of a variety of manufacturing processesas are well known to those of skill in the art, including injectionmolding, and vacuum forming. In addition, the housing 41 may be madefrom any of a variety of materials, including but not limited toplastic, metal, glass, rubber, and ceramic, or a combination thereof. Inone embodiment the housing 41 includes removable portions (not shown)that may be interchanged with other removable portions of differentcolor, or containing different logos, pictures, or symbols.

The display 30 of exemplary display device 40 may be any of a variety ofdisplays, including a bi-stable display, as described herein. In otherembodiments, the display 30 includes a flat-panel display, such asplasma, EL, OLED, STN LCD, or TFT LCD as described above, or anon-flat-panel display, such as a CRT or other tube device, as is wellknown to those of skill in the art. However, for purposes of describingthe present embodiment, the display 30 includes an interferometricmodulator display, as described herein.

The components of one embodiment of exemplary display device 40 areschematically illustrated in FIG. 6B. The illustrated exemplary displaydevice 40 includes a housing 41 and can include additional components atleast partially enclosed therein. For example, in one embodiment, theexemplary display device 40 includes a network interface 27 thatincludes an antenna 43 which is coupled to a transceiver 47. Thetransceiver 47 is connected to the processor 21, which is connected toconditioning hardware 52. The conditioning hardware 52 may be configuredto condition a signal (e.g. filter a signal). The conditioning hardware52 is connected to a speaker 45 and a microphone 46. The processor 21 isalso connected to an input device 48 and a driver controller 29. Thedriver controller 29 is coupled to a frame buffer 28 and to the arraydriver 22, which in turn is coupled to a display array 30. A powersupply 50 provides power to all components as required by the particularexemplary display device 40 design.

The network interface 27 includes the antenna 43 and the transceiver 47so that the exemplary display device 40 can communicate with one oremore devices over a network. In one embodiment the network interface 27may also have some processing capabilities to relieve requirements ofthe processor 21. The antenna 43 is any antenna known to those of skillin the art for transmitting and receiving signals. In one embodiment,the antenna transmits and receives RF signals according to the IEEE802.11 standard, including IEEE 802.11 (a), (b), or (g). In anotherembodiment, the antenna transmits and receives RF signals according tothe BLUETOOTH standard. In the case of a cellular telephone, the antennais designed to receive CDMA, GSM, AMPS or other known signals that areused to communicate within a wireless cell phone network. Thetransceiver 47 pre-processes the signals received from the antenna 43 sothat they may be received by and further manipulated by the processor21. The transceiver 47 also processes signals received from theprocessor 21 so that they may be transmitted from the exemplary displaydevice 40 via the antenna 43.

In an alternative embodiment, the transceiver 47 can be replaced by areceiver. In yet another alternative embodiment, network interface 27can be replaced by an image source, which can store or generate imagedata to be sent to the processor 21. For example, the image source canbe a digital video disc (DVD) or a hard-disc drive that contains imagedata, or a software module that generates image data.

Processor 21 generally controls the overall operation of the exemplarydisplay device 40. The processor 21 receives data, such as compressedimage data from the network interface 27 or an image source, andprocesses the data into raw image data or into a format that is readilyprocessed into raw image data. The processor 21 then sends the processeddata to the driver controller 29 or to frame buffer 28 for storage. Rawdata typically refers to the information that identifies the imagecharacteristics at each location within an image. For example, suchimage characteristics can include color, saturation, and gray-scalelevel.

In one embodiment, the processor 21 includes a microcontroller, CPU, orlogic unit to control operation of the exemplary display device 40.Conditioning hardware 52 generally includes amplifiers and filters fortransmitting signals to the speaker 45, and for receiving signals fromthe microphone 46. Conditioning hardware 52 may be discrete componentswithin the exemplary display device 40, or may be incorporated withinthe processor 21 or other components.

The driver controller 29 takes the raw image data generated by theprocessor 21 either directly from the processor 21 or from the framebuffer 28 and reformats the raw image data appropriately for high speedtransmission to the array driver 22. Specifically, the driver controller29 reformats the raw image data into a data flow having a raster-likeformat, such that it has a time order suitable for scanning across thedisplay array 30. Then the driver controller 29 sends the formattedinformation to the array driver 22. Although a driver controller 29,such as a LCD controller, is often associated with the system processor21 as a stand-alone Integrated Circuit (IC), such controllers may beimplemented in many ways. They may be embedded in the processor 21 ashardware, embedded in the processor 21 as software, or fully integratedin hardware with the array driver 22.

Typically, the array driver 22 receives the formatted information fromthe driver controller 29 and reformats the video data into a parallelset of waveforms that are applied many times per second to the hundredsand sometimes thousands of leads coming from the display's x-y matrix ofpixels.

In one embodiment, the driver controller 29, array driver 22, anddisplay array 30 are appropriate for any of the types of displaysdescribed herein. For example, in one embodiment, driver controller 29is a conventional display controller or a bi-stable display controller(e.g., an interferometric modulator controller). In another embodiment,array driver 22 is a conventional driver or a bi-stable display driver(e.g., an interferometric modulator display). In one embodiment, adriver controller 29 is integrated with the array driver 22. Such anembodiment is common in highly integrated systems such as cellularphones, watches, and other small area displays. In yet anotherembodiment, display array 30 is a typical display array or a bi-stabledisplay array (e.g., a display including an array of interferometricmodulators).

The input device 48 allows a user to control the operation of theexemplary display device 40. In one embodiment, input device 48 includesa keypad, such as a QWERTY keyboard or a telephone keypad, a button, aswitch, a touch-sensitive screen, a pressure- or heat-sensitivemembrane. In one embodiment, the microphone 46 is an input device forthe exemplary display device 40. When the microphone 46 is used to inputdata to the device, voice commands may be provided by a user forcontrolling operations of the exemplary display device 40.

Power supply 50 can include a variety of energy storage devices as arewell known in the art. For example, in one embodiment, power supply 50is a rechargeable battery, such as a nickel-cadmium battery or a lithiumion battery. In another embodiment, power supply 50 is a renewableenergy source, a capacitor, or a solar cell, including a plastic solarcell, and solar-cell paint. In another embodiment, power supply 50 isconfigured to receive power from a wall outlet.

In some implementations control programmability resides, as describedabove, in a driver controller which can be located in several places inthe electronic display system. In some cases control programmabilityresides in the array driver 22. Those of skill in the art will recognizethat the above-described optimization may be implemented in any numberof hardware and/or software components and in various configurations.

The details of the structure of interferometric modulators that operatein accordance with the principles set forth above may vary widely. Forexample, FIGS. 7A-7E illustrate five different embodiments of themovable reflective layer 14 and its supporting structures. FIG. 7A is across section of the embodiment of FIG. 1, where a strip of metalmaterial 14 is deposited on orthogonally extending supports 18. In FIG.7B, the moveable reflective layer 14 is attached to supports at thecorners only, on tethers 32. In FIG. 7C, the moveable reflective layer14 is suspended from a deformable layer 34, which may comprise aflexible metal. The deformable layer 34 connects, directly orindirectly, to the substrate 20 around the perimeter of the deformablelayer 34. These connections are herein referred to as support posts. Theembodiment illustrated in FIG. 7D has support post plugs 42 upon whichthe deformable layer 34 rests. The movable reflective layer 14 remainssuspended over the cavity, as in FIGS. 7A-7C, but the deformable layer34 does not form the support posts by filling holes between thedeformable layer 34 and the optical stack 16. Rather, the support postsare formed of a planarization material, which is used to form supportpost plugs 42. The embodiment illustrated in FIG. 7E is based on theembodiment shown in FIG. 7D, but may also be adapted to work with any ofthe embodiments illustrated in FIGS. 7A-7C as well as additionalembodiments not shown. In the embodiment shown in FIG. 7E, an extralayer of metal or other conductive material has been used to form a busstructure 44. This allows signal routing along the back of theinterferometric modulators, eliminating a number of electrodes that mayotherwise have had to be formed on the substrate 20.

In embodiments such as those shown in FIG. 7, the interferometricmodulators function as direct-view devices, in which images are viewedfrom the front side of the transparent substrate 20, the side oppositeto that upon which the modulator is arranged. In these embodiments, thereflective layer 14 optically shields some portions of theinterferometric modulator on the side of the reflective layer oppositethe substrate 20, including the deformable layer 34 and the busstructure 44. This allows the shielded areas to be configured andoperated upon without negatively affecting the image quality. Thisseparable modulator architecture allows the structural design andmaterials used for the electromechanical aspects and the optical aspectsof the modulator to be selected and to function independently of eachother. Moreover, the embodiments shown in FIGS. 7C-7E have additionalbenefits deriving from the decoupling of the optical properties of thereflective layer 14 from its mechanical properties, which are carriedout by the deformable layer 34. This allows the structural design andmaterials used for the reflective layer 14 to be optimized with respectto the optical properties, and the structural design and materials usedfor the deformable layer 34 to be optimized with respect to desiredmechanical properties.

FIG. 8 shows an embodiment of a display device 125 comprising an arrayof interferometric modulators configured to perform substantially as aspecular mirror in addition to displaying information. At least aportion of the array may be configured to be specular, e.g.,mirror-like, instead of diff-use as is the case for many embodiments ofinterferometric modulators. Generally an interferometric modulator is aspecular device. In one modulator embodiment the interferometricmodulator appears diffuse only if a diffusion material is used to modifythe incident and reflected light. When a diffusion material is not usedthe array appears substantially specular. The reflective layer withinthe interferometric modulator is substantially specular and theinterferometric properties of the cavity and the optical stack may beconfigured so that the entire interferometric modulator is alsospecular. At least a portion of the array may be configured to be white(e.g. reflective of light across the visible spectrum), instead ofcolored (e.g. reflective of light within a narrow or wide band ofvisible wavelengths or reflective of light within multiple narrow orwide bands of visible wavelengths, but not across the entire visiblespectrum), as is the case for many embodiments of interferometricmodulators. In addition to being substantially specular, the reflectivelayer within the interferometric modulator is also substantially white,and the interferometric properties of the cavity and the optical stackmay be configured so that the entire interferometric modulator is alsowhite. Techniques for accomplishing whiteness and specularity include,but are not limited to those briefly discussed herein. In general, ifthe optical stack is sufficiently thin, it will not significantly alterthe whiteness of the device. Specifics will depend at least on materialsused. Some embodiments of interferometric modulators with thin opticalstacks have the electronic control and the mechanical structure onopposite side of the deflectable mirror than the optical stack. Thisallows the thickness of the optical stack to be controlled independentof constraints incurred when the electrode is embedded within theoptical stack. Another option to whiten the device is to create theinterferometric cavities with gaps large enough to allow multiplefrequencies of light to constructively interfere.

In some embodiments at least a portion of the display device 125 may beconfigured to display information. The interferometric modulators insuch a portion can be configured to selectably change between at leasttwo optical states according to an input, as described above. Theoptical characteristics of the at least two states differ enough so thata contrast between the states can be perceived by a viewer. When theoptical characteristics of individual interferometric modulators areproperly selected, the information can be displayed. The opticalcharacteristics which may be selectably altered include reflectivity,and color. For example, to display information certain interferometricmodulators may be selected to have higher reflectivity than otherinterferometric modulators, or certain interferometric modulators may beselected to have blue color and others green color, where the differencebetween the higher and lower reflectivity, and the blue and green coloris at least enough to be perceived by a viewer. Combinations of opticalcharacteristics may be used. For example, combinations of colors andreflectivity may be altered to create perceptible contrast. Othercontrasting optical characteristic states are possible and are notdisfavored. Thus, the ability to selectably alter the interferometricmodulators contrasting optical states allows for text or an image to bedisplayed.

In some embodiments at least a portion of the display portion 120 may beconfigured to change between first and second optical states, while asecond portion may be configured to change between third and fourthoptical states. In some embodiments these portions are continuous andlarge enough to be seen by a viewer as being distinct areas where theeach area is perceived as having a distinct optical characteristic. Forexample, a region may have the shape of a sun, and the interferometricmodulators in the region may have a color characteristic of reflectingyellow light. Some of the interferometric modulators in the region mayalso selectably change between reflecting yellow light and reflectingwhite light. The selectably changeable interferometric modulators may beused to, for example, display a current temperature.

In some embodiments the interferometric modulators may operate over arange of optical states, such as a continuous range of colors orgrey-scale or reflectivity. The display portion 120 may also be a colordisplay wherein each pixel can selectively display a range of colors.The display portion 120 may also display in a grey scale mode where theinterferometric modulators are configured to be white, and how muchreflectivity in each pixel varies according to the information to bedisplayed. The display device 125 may have various display portions 120which may each have different operating configurations as describedabove. In some embodiments the operating configuration of the displayportions may change.

As discussed above, in some embodiments the information is displayed bythe contrast of two optical states both being reflective. In suchembodiments it should be noted that the display portion 120 in additionto displaying information is specularly reflective and will stillfunction as a mirror. For example if a portion of the display portion isdisplaying information using interferometric modulators configured tochange between orange and green reflective states that portion of thedisplay device 125 will still show the image of objects seen in themirror. The objects, however, will appear as if they are orange and/orgreen.

In some embodiments the display portion 120 may have interferometricmodulators which are formed in a specific shape corresponding to theinformation or a portion of the information to be displayed. For examplethe display portion 120 may have an interferometric modulator in theshape of a vehicle with a door open. Such an interferometric modulatormay be used on a rear-view mirror in a vehicle. A door not beingcompletely closed may be indicated by actuating the interferometricmodulator such as to have a contrasting appearance to the immediatelysurrounding area of the mirror. Some interferometric modulators may bein the shape of numeral segments, so as to be configured to, incombination, display various numerals.

In some embodiments a diffusion material is applied to at least aportion of the array to render that portion of the display more diffusethan other portions. For example, one or more portions of the device maybe dedicated as display-only portions, where better display appearancemay be attained with a diffusion material.

Alternatively, one or more portions may be dedicated as mirror-onlyportions. In mirror-only portions the interferometric modulators may beconfigured to be in a single non-selectable state of having white coloras perceived by a viewer and/or having high reflectivity (i.e. beingreflective enough to effectively useable as a mirror). The regionsbetween interferometric modulators may also be configured to have highreflectivity. In some embodiments the mirror-only portions may comprisereflective layers only and may not comprise interferometric modulators.In some embodiments the mirror-only portion may have optical stackproperties customized for high reflectivity.

Referring to FIG. 8, a mirror surface 130 of a display device 125 may beused for any purpose for which mirrors are used, such as shaving orapplying makeup. Simultaneously, a display portion 120 of the displaydevice 125 may be used to provide information to a viewer. The displayportion 120 may be of any shape, may be located at any position of thedisplay device 125, and may be moved from position to position. Suchmanipulation of the display portion 120 may be controlled, for exampledynamically by user input, or through programming, or another externaldevice. Although shown in FIG. 8 as being rectangular the display device125 may be of arbitrary shape.

The information may include any type of desired information includingbut not limited to news, stock quotations, sports scores etc. Forexample, while combing ones hair, information about the weather forecastmay be displayed to help in deciding what clothing to wear for the day.The information may be communicated to the display device 125 from anexternal source, such as, but not limited to a telecommunications ordisplay device over a wired or wireless connection. For example, thedisplay device 125 may comprise or have a wired or wireless connectionto a device with a television tuner, and the display may show themorning news or a sporting event. The display device 125 may alsocomprise or have an electrical connection to a PC, or a device fordisplaying video images, such as a video player, or a DVD player. Insome embodiments the PC may be connected to an internet site showinglive images of, for example, traffic conditions or a place of interestin natural setting such as a waterfall.

One or more aspects of the information may be programmable. The displaydevice 125 may, for example, sequentially display current outsidetemperature, expected high temperature and expected low temperature forthe day. The user may program the display device 125 to display one ormore types of information from a set of optional information types, suchas sports scores, news headlines, or driving conditions. The informationmay be primarily aesthetic, such as an ornamental design or a picture ofones family. The information may be user defined, such as a “to do”list, or a reminder of a friends birthday. The display device 125 may beconfigured to have various modes of operation from which the userchooses. For example, the user may select a mode to display aestheticimages or to display traffic information or to display combinations ofinformation types.

The user programmability may be managed in various ways. There may be awireless or wired connection to a PC with software to program thedisplay device 125. The display device 125 may comprise local processingcapabilities with software to enable the user to interface graphicallywith the associated programming software. There may be an interface forthe user to connect a keyboard and/or a mouse to the display device 125at least for programming. In some embodiments the display device 125 maycomprise touch screen technology, which may at least be used forprogramming. In some embodiments the display device 125 may comprisebuttons and/or knobs for programming and/or for controlling displaycharacteristics, such as location or brightness.

In some embodiments, the display device 125 is configured as a rear-viewor side mirror on a vehicle. Such an embodiment is shown as rear-viewmirror 150 in FIG. 9. Using interferometric modulator technology, themirror can display information to the driver. The information mayinclude environmental information, such as temperature, wind speed andwind direction. Location data, such as position, speed, and direction oftravel may also be shown. Route information may be given, such as a map,turn by turn driving directions, and direction of and distance to thenext turn. Vehicle status data, such as speed, temperature, engine RPM,the distance to objects behind the car, an image of what is behind thecar may also be displayed. Radio information, such as volume, channel,CD title, song title, and program title may also be displayed. Variouswarnings, such as low fuel, high speed, high engine temperature,passenger without a seatbelt, low tire pressure, and external objectproximity. Various sensors throughout the vehicle may be configured tocommunicate to the display device 125 to provide the information to bedisplayed. The information may also be communicated from externalsources using wireless connections.

The mirror may also be configured with a mount to attach the mirror to avehicle, a wall, an article of furniture, an ornamental object, anarticle of clothing, or a person.

While the above detailed description has shown, described, and pointedout novel features as applied to various embodiments, it will beunderstood that various omissions, substitutions, and changes in theform and details of the device or process illustrated may be made bythose skilled in the art without departing from the spirit of theinvention. As will be recognized, the present invention may be embodiedwithin a form that does not provide all of the features and benefits setforth herein, as some features may be used or practiced separately fromothers.

1. A device, comprising: a substrate; and an array of reflectiveelements arranged on the substrate to form at least a portion of amirror surface that specularly reflects incident light in at least onewavelength band, each element comprising: a partially reflective layer;and a substantially reflective layer separated from the partiallyreflective layer by a predetermined space, wherein the space defines aninterferometric cavity; wherein one or more of the elements areconfigured to be selectably reflective.
 2. The device of claim 1,wherein one or more of the selectably reflective elements is configuredto selectably be in one of first and second optical states.
 3. Thedevice of claim 2, wherein the first optical state differs from secondoptical state in at least one of reflectivity and color so that thecontrast between the two states is perceptible to a viewer.
 4. Thedevice of claim 1, wherein one or more of the elements are configured tobe in a single non-selectable state of being highly reflective.
 5. Thedevice of claim 4, wherein at least a portion of the area between theelements configured to be in a single non-selectable state of highreflectivity is configured to be specularly reflective.
 6. The device ofclaim 1, wherein at least a portion of the reflective surface of themirror comprises a highly reflective layer configured to reflectnon-interferometrically.
 7. The device of claim 1, wherein at least oneof the reflective elements of the array is formed in a shapecorresponding to at least a portion of the information to be displayedby the at least one element.
 8. The device of claim 1, wherein at leasta portion of the area between the elements of the array is configured tobe specularly reflective.
 9. The device of claim 1, wherein at least afirst portion of the array comprises adjacent elements configured to beperceived by a viewer as displaying an optical characteristic differentfrom an optical characteristic displayed by another portion of thearray.
 10. The device of claim 1, wherein at least at least one of theselectably reflective elements is configured to be perceived as:displaying information; and being highly reflective.
 11. The device ofclaim 1, wherein the optical characteristics of one or more of theelements is based upon at least one of input from an external source,user input, and programming.
 12. The device of claim 1, wherein one ormore of the elements are configured to be reflective across the visiblespectrum.
 13. The device of claim 1, wherein one or more of the elementsare configured to reflect light substantially of a different wavelengthband than one or more other elements.
 14. The device of claim 1, furthercomprising: a processor that is in electrical communication with thearray, the processor being configured to process image data; and amemory device in electrical communication with the processor.
 15. Thedevice of claim 14, further comprising a driver circuit configured tosend at least one signal to the array.
 16. The device of claim 15,further comprising a controller configured to send at least a portion ofthe image data to the driver circuit.
 17. The device of claim 14,further comprising an image source module configured to send the imagedata to the processor.
 18. The device of claim 17, wherein the imagesource module comprises at least one of a receiver, transceiver, andtransmitter.
 19. The device of claim 14, further comprising an inputdevice configured to receive input data and to communicate the inputdata to the processor.
 20. A vehicle comprising: a steering mechanism;and a mirror configured to be positioned such that light coming frombehind the vehicle is reflected to a location for an operator to seewhen positioned to use the steering mechanism, the mirror comprising: asubstrate; and an array of reflective elements arranged on the substrateto form a mirror surface that specularly reflects incident light in atleast one wavelength band, each element comprising: a partiallyreflective layer; and a substantially reflective layer separated fromthe partially reflective layer by a predetermined space, wherein thespace defines an interferometric cavity.
 21. The vehicle of claim 20,wherein the mirror is configured to display warnings, radio information,vehicle status data, route information, location data, or environmentalinformation.
 22. The vehicle of claim 20, wherein one or more of thereflective elements is configured to selectably be in one of first andsecond optical states.
 23. The vehicle of claim 20, wherein one or moreof the reflective elements are configured to be in a singlenon-selectable state of being highly reflective.
 24. The vehicle ofclaim 20, wherein at least a portion of the reflective surface of themirror comprises a highly reflective layer configured to reflectnon-interferometrically.
 25. The vehicle of claim 20, wherein at leastone of the reflective elements is formed in a shape corresponding to atleast a portion of the information to be displayed by the at least oneelement.
 26. The vehicle of claim 20, wherein the opticalcharacateristics of one or more of the reflective elements is based uponat least one of input from an external source, user input, andprogramming.
 27. A device comprising: a mirror comprising: a substrate;and an array of reflective elements arranged on the substrate to form amirror surface that specularly reflects incident light in at least onewavelength band, each element comprising: a partially reflective layer;and a substantially reflective layer separated from the partiallyreflective layer by a predetermined space, wherein the space defines aninterferometric cavity and the wavelength band of light reflected fromthe element is based on a dimension of the cavity; and a mountconfigured to attach the mirror to a vehicle, a wall, an article offurniture, an ornamental object, an article of clothing, or a person.28. The device of claim 27, wherein one or more of the elements areconfigured to be in a single non-selectable state of being highlyreflective.
 29. The device of claim 27, wherein at least a first portionof the array comprises adjacent elements configured to be perceived by aviewer as displaying an optical characteristic different from an opticalcharacteristic displayed by another portion of the array.
 30. The deviceof claim 27, wherein optical characteristics of one or more of theelements is based upon at least one of input from an external source,user input, and programming.
 31. The device of claim 27, wherein one ormore of the elements are configured to be reflective across the visiblespectrum.
 32. The device of claim 27, wherein one or more of theelements are configured to reflect light substantially of a differentwavelength band than one or more other elements.
 33. A mirror device,comprising: means for interferometrically and specularly reflectingincident light in at least one wavelength band; and means for selectablyand interferometrically reflecting incident light in at least onewavelength band.
 34. The device of claim 33 wherein theinterferometrically and specularly reflecting means and the selectablyand interferometrically reflecting means each comprise an array ofreflective elements arranged on the substrate to form a mirror surfacethat specularly reflects incident light in at least one wavelength band,each element comprising: a partially reflective layer; and asubstantially reflective layer separated from the partially reflectivelayer by a predetermined space, wherein the space defines aninterferometric cavity.
 35. The device of claim 33, further comprisingmeans for selecting the optical characteristics of a portion of theselectably and interferometrically reflecting means based upon at leastone of input from an external source, user input, and programming.. 36.The device of claim 35, wherein the selecting means for selectingcomprises a driving circuit.
 37. The device of claim 33, wherein a firstportion of the selectably and interferometrically reflecting means isconfigured to reflect light substantially of a different wavelength bandthan a second portion of the selectably reflecting means.
 38. A methodof using a display device comprising: establishing a communication linkbetween the device and an information source, the device comprising amirror comprising a substrate; and an array of reflective elementsarranged on the substrate to form a mirror surface that specularlyreflects incident light in at least one wavelength band, each elementcomprising: a partially reflective layer; and a substantially reflectivelayer separated from the partially reflective layer by a predeterminedspace, wherein the space defines an interferometric cavity and thewavelength band of light reflected from the element is based on adimension of the cavity; and a mount configured to attach the mirror toa vehicle, a wall, an article of furniture, an ornamental object, anarticle of clothing, or a person; receiving information from the source;and displaying the information on the array.
 39. The method of 38,wherein displaying the information comprises displaying the informationbased upon at least one of input from an external source, user input,and programming.
 40. The method of claim 38, wherein displaying theinformation comprises selecting states for the selectably reflectiveelements, wherein the elements are configured to selectably be in one offirst and second optical states.
 41. The method of claim 40, wherein atleast one of the elements for which a state is selected has a shapecorresponding to at least a portion of the information to be displayedby the at least one element.
 42. The method of claim 38, whereindisplaying the information comprises: displaying a first opticalcharacteristic on a first portion of the array; and displaying a secondoptical characteristic on a second portion of the array.
 43. A method ofmanufacturing a device comprising: forming a substrate; and forming anarray of reflective elements arranged on the substrate so as to producea mirror surface that specularly reflects incident light in at least onewavelength band, each element comprising: a partially reflective layer;a substantially reflective layer separated from the partially reflectivelayer by a predetermined space, wherein the space defines aninterferometric cavity; and wherein one or more of the elements areconfigured to be selectably reflective.
 44. The method of claim 43,wherein forming the array comprises configuring the elements to beselectably reflective based upon at least one of input from an externalsource, programming, and user input.
 45. The method of claim 43, whereinforming the array comprises configuring one or more of the elements tobe reflective across the visible spectrum.
 46. The method of claim 43,wherein forming the array comprises configuring one or more of theelements to reflect light substantially of a different wavelength bandthan one or more other elements.
 47. A device manufactured by the methodof claim 43